The Research Of Near-infrared Detection And Imaging Of PbS Colloidal Quantum Dot Photodetector

PbS colloidal quantum dot is a kind of important opto-electronic material.Compared with traditional epitaxially grown infrared detection materials,PbS colloidal quantum dots which can meet the requirements of low-cost,high-performance,and room temperature operation of the next-generation infrared detectors have many advantages,including low-cost synthesis,multi-substrate compatibility,non-flip-chip process.Showing excellent application prospects in the visible and near-infrared spectra,PbS colloidal quantum dots are considered as strong candidates for the next-generation infrared detection materials.However,near-infrared photodetectors based on PbS colloidal quantum dots still have key problems such as low responsivity and large dark current.In this paper,the PbS CQR NIR photodetector with the first exciton absorption peak at 1061 nm is considered as the research object.The photodiode and photo field effect transistor devices are designed and fabricated,respectively.The performance evaluation and comparison between two devices are carried out.Finally,the optimization process of the photodiode device is mainly studied.The research results obtained in the thesis are as follows:（1）PbS colloidal quantum dots with a first exciton absorption peak at 1061 nm were synthesized by hot injection method.The absorption peak of PbS colloidal quantum dots was extended to 1800 nm by optimized multiple hot injection method.The preparation of photodiode and photo-FET photodetector based on solid-phase ligand exchange process was completed.Then,photodiode with faster response time,lower dark current and higher switching ratio were selected for near-infrared imaging research.The responsivity R and normalized detectivity D^*of the photodiode device are 0.07 A/W,2.1×10¹¹ Jones,respectively.（2）Liquid-phase ligand exchange was then used to replace the traditional solid-phase ligand exchange,and photodiode based on PbS quantum dot ink was fabricated.Under the premise that the thickness of the absorber layer and the structure of the device remained unchanged,the responsivity of the optimized PbS-Ink device was increased to 0.24 A/W,which is 240%higher than that of the original device based on SSLE.Aiming at the problem of dark current suppression in quantum dot ink devices,an innovative method for regulating the physical thickness of the PbS-EDT electronic barrier layer is proposed,which passivates the defects of the barrier layer,reduces the trap-assisted injection current,and reduces the dark current of the device.The dark current density of the optimized device was 2 orders of magnitude lower than the device in part 2 from 1×10⁵ n A/cm² to 1.9×10³ n A/cm².（3）Innovatively,the passivation of PbS-EDT electronic barrier layer by 1,2-EDT acetonitrile solution treatment with different concentrations was studied.Influenced by the influence of the device energy level adjustment and arrangement,the separation and transport of photogenerated carriers are promoted,the response time of the device is reduced from 69.8μs to 50.8μs,and the dark current of the device is further reduced to 22.40 n A/cm².Finally,a low-noise,high-response quantum dot infrared detector is obtained,and an active low-light imaging demonstration is realized.To sum up,this thesis studies the PbS colloidal quantum dot photodetector with an absorption peak of 1061 nm,and uses near-infrared imaging as a traction to fabricate photodiodes and photo-FET detectors,and explores an effective method for responsivity optimization,dark current suppression,and response speed improvement.Finally,a new process for stably preparing high-performance and stable photodiode detectors is developed.Based on this process,high-performance near-infrared low-light imaging is obtained and the research near-infrared detection devices in the future is broadened.